1. Field of the Invention
The invention relates to a loudspeaker system comprising an enclosure which accommodates a loudspeaker device and a bass-reflex port having two open ends, this port having a longitudinal axis and a length defined by the two open ends, and having a passage which flares towards the two open ends, flared portions being present, these flared portions extending over a substantial part of the length of the port.
2. Description of the Related Art
A bass-reflex port is essentially an open duct by means of which an internal volume of a loudspeaker enclosure communicates with the medium outside the enclosure, a first open end being situated inside the enclosure and a second open end being situated outside the enclosure. Such a port enhances the sound reproduction in the lower range of the frequency spectrum. The effect of the bass-reflex port is based on the Helmholtz resonator principle, which is known per se, the frequency of the reproduced sound being dependent on the volume of the enclosure, the length and cross-section of the port and the velocity of sound. Small loudspeaker enclosures require a port of comparatively small cross-section. However, in order to obtain the same sound pressure at or near the Helmholtz frequency in a small enclosure as in a large enclosure, it is necessary that, per unit of time, the same amount of air flows through the port. This means that the flow velocity of the air in the port is comparatively high for a small enclosure. It has been found that when known bass-reflex ports are used, these ports having a constant cross-section, a high sound level at or near the Helmholtz frequency is accompanied by noises, acoustic losses and distortions of the sound.
International Application WO-A 90/11668 discloses a loudspeaker system, which comprises a bass-reflex cabinet with a loudspeaker and a duct. The duct provides the communication between the interior and the exterior of the cabinet and constitutes an adapter of converging-diverging longitudinal section. Shapes proposed for the adapter are conical, exponential and hyperbolic profiles, the asymptote to the adapter being required to extend at an angle of between 30.degree. and 50.degree. with respect to the longitudinal direction. The adapter used in the known loudspeaker system serves to take the place of a duct of constant cross-section.